1. Field of the Invention
Embodiments of the present invention relate to a technique for correcting chromatic aberration of magnification on image data.
2. Description of the Related Art
Conventionally, techniques for correcting chromatic aberration of magnification caused by an imaging optical system have been known. In the technique discussed in Japanese Patent Application Laid-Open No. 2008-015946, in order to correct chromatic aberration of magnification, first, a video signal captured by an image sensor including a color filter of a Bayer array is separated into red (R) components, green (G) components, and blue (B) components. Then, a pixel value of a pixel that does not contain the R component is interpolated by adjacent pixels of the R components, so that an interpolation R component is generated. A pixel value of a pixel that does not contain the B component is interpolated by adjacent pixels of the B components, so that an interpolation B component is generated.
After the processing, a circuit for correcting chromatic aberration of magnification performs correcting chromatic aberration of magnification by replacing each pixel value of the interpolation R components with a pixel value expected to be there when the G components are used as a reference. Further, if the position of the pixel to be replaced with the pixel value expected to be there is deviated by less than one pixel from the pixel values of the peripheral R components, by interpolating the deviation of less than one pixel from the pixel values of the peripheral R components, the pixel value to be replaced is calculated. On the interpolation of B components, similar replacement is performed. Further, the pixel positions of the interpolation R components and the interpolation B components are corrected with respect to the G components, so that the chromatic aberration of magnification is corrected.
The R components, B components, and G components whose chromatic aberrations of magnification are corrected are then subjected to image quality adjustment processing, such as gamma correction and aperture correction, and the components are converted into luminance components and color difference components. When the color difference components are generated, false color suppression processing is performed such that aliasing around the Nyquist frequency does not appear as a false signal in the image.
Meanwhile, a technique for reducing noise by dividing an image signal into a plurality of frequency bands and performing frequency synthesis on the image signals processed in each frequency band has been known. For example, in the technique discussed in Japanese Patent Application Laid-Open No. 2008-015741, while preserving edge components in each of n frequency bands, noise components are reduced, so that only the noise components may be reduced while the wide band edge components are being preserved.
By applying the above-described techniques, it is assumed that the image quality adjustment processing, such as the gamma correction and the aperture correction, is performed by performing the correction of chromatic aberration of magnification, and then the luminance components and the color difference components are output by performing the noise reduction processing while performing the false suppression processing.
However, in such a technique on the above-described assumption, the band-limited image signals need to be stored in many planes in a memory including a dynamic random access memory (DRAM), or the like. Further, the image signals of each plane need to be stored for each frequency component. Therefore, in a case of processing requiring high-speed performance, such as continuous shooting, if a memory access amount per unit time increases and reaches an upper limit of the memory access band, the processing performance decreases. Further, the increase in the necessary memory capacity will cause increase in the cost of the image processing apparatus.